1. Field of the Invention
The present invention relates to a method of circulating a heat transfer medium fluid, such as a heating medium or a cooling medium, through a plurality of hot plate like heat conducting plates which constitute a caterpillar. The present invention further relates to a plate treating apparatus using such a caterpillar.
2. Prior Art
Heretofore, to dry a veneer there have been proposed drying methods using various devices: for example, a dryer circulating hot air transversely or longitudinally of the veneer; a multiplaten press having hot plates vertically or laterally arranged, the hot plates being supplied with a heating medium such as steam, hot oil and warm water; a single platen press having hot plates disposed in a single layer; a continuous press having a steel belt, a mesh belt or a metallic sheet wound around each hot plate in an endless shape; a continuous press having endless chains extended around recesses formed in a pair in an outer surface of a hot plate; and a slat conveyor type press using narrow hot plates.
Dryers are widely used for drying veneers. It is well known that in terms of heat efficiency, a single stage press and a multistage press, which bring hot plates into direct contact with a veneer, are superior to an indirect heating dryer circulating hot air over surfaces of veneer. However, such presses are disadvantageous in that mechanisms to convey a veneer to and away from the hot plates are rather complicated, and in that the veneer is liable to be damaged in moving to and away from the hot plates.
In the continuous press, a veneer is placed on an endless steel belt or a pair of chain conveyers and is turned around to move to a position above a hot plate. After heat dried, the veneer is carried away by turning the steel belt or the chain conveyors. In this manner, automatic carrying in and out of the veneer is achieved. When a belt like member, such as a steel belt, is used in the veneer transporting mechanism, the hot plate makes an indirect heat contact with a veneer for heating, resulting in a low heat efficiency. Moreover, such a heating operation can cause the belt like member to be damaged with the lapse of time. In the veneer transporting mechanism using a pair of chain conveyors, an elevating mechanism is needed. The elevating mechanism is actuated to elevate the chain conveyors or a hot plate every time when a veneer is placed on or taken away from the chain conveyors, and when the veneer is brought into contact with the surface of the hot plate. This is because the veneer is turned over while transported by the conveyors.
In the slat conveyor type press, a group of slats are heated, and hence burners, heaters and like devices are arranged at predetermined positions near the caterpillar for indirect heating of a veneer.